Since the successful development of high activity polyethylene catalyst at 1970s, the whole polyethylene industry in the world has changed greatly. In recent three decades, with the development of ethylene polymerization processes, catalysts assorting to the polymerization processes have gotten significant progress, and high activity catalysts have been playing an important role in the field of polyethylene catalyst because of their excellent polymerization performance and mature application technology. Through many years of research, the preparation process of Mg—Ti-based high activity catalysts has developed to chemical reaction process from co-grinding process and suspension-impregnation process. Among the chemical reaction processes, many patents, for example, EP 688794(CN1158136) and U.S. Pat. Nos. 3,787,384; 4,148,754; 4,173,547; 4,301,029; 4,508,843; 4,921,920 and 5,124,296, direct to catalysts obtained by supporting the reaction product, as active component, of a dihydrocarbyl magnesium, a chlorinating agent and a transition metal halide etc. onto a spheric inorganic oxide support. The recent development on this type of Mg—Ti-based catalyst is introduction of electron donor compound (for example aliphatic alcohol compounds) during the preparation of the catalyst composition. Experiments show that the introduction of the electron donor compound improves polymerization activity and hydrogen response of the catalyst.
For example, EP688794 discloses use of a long chain aliphatic alcohol compound having α-branch chain during the preparation of the catalyst composition, and polymerization activity and hydrogen response of the catalyst are improved by introducing said compound. In particular, said catalyst retains high polymerization activity under different hydrogen partial pressures for preparing ethylene homopolymer and copolymer having low and high molecular weight, namely, the balance of the activity of the catalyst is good. However, the inventors have now found that such catalyst solid component powders carry a great amount of static charges, so that an anti-static agent must be added in the polymerization process, thus operation is discommodious and cost increases. While without limited to any specific theory, the inventors believe after repeated experiments that the addition of alkyl metal chloride compound in the preparation of the catalyst is a main reason resulting in that the catalyst solid component powders carry a great amount of static charges.
After repeated experiments, the inventors have now found that a catalyst solid component prepared by using an alkyl metal compound in combination with a difunctional compound having a specific structure and a halide rather than alkyl metal chloride compound solves the problem that catalyst solid component powders carry too great amount of static charges, and the catalyst powders exhibit excellent flowability, good hydrogen response and co-polymerization performance, and high polymerization activity.